1. Field of the Invention
This invention relates to a method for the purification of homogeneous iron complex catalyzed organic reaction products.
2. Description of the Prior Art
Homogeneous iron catalysts; i.e., organic soluble iron in the form of covalently bonded complexes thereof, are widely used in the chemical industry for catalyzing a variety of reactions. Although iron complexes of this type are used in relatively small amounts to effect catalysis, they must be removed if not only because of the intense objectionable coloration these species impart to the final product and because their presence imparts chemical instability to the products. Moreover, many of the indicated products are chemical intermediates whose specifications and end use requirements frequently exclude the presence of all but trace amounts of iron.
In a number of instances the organic product of the catalysis reaction can be readily distilled to accomplish purification thereof. On the other hand there are likewise numerous instances where a distillation operation does not represent a viable expedient due to the relatively high vapor pressure of the homogeneous iron catalyst and the resultant codistillate. Also, in some situations it is not feasible to accomplish the degree of purification required by distillation since the organic products are temperature unstable and frequently cannot survive the long temperature exposures required for fractional distillation.
Heretofore, it has been proposed to rid reaction products of their spent organic soluble iron catalyst values by the addition of formic acid and hydrogen proxide so as to generate performic acid in situ. The latter reacts with the iron impurities to form water-soluble species thereof which can be readily removed by a convenient washing operation. This prior art method is effective but suffers because the relatively large amount of performic acid involved in high volume commercial production operations poses potentially hazardous conditions due to the thermodynamic instability of this reactant.